Liquid crystal panel inspection method

Abstract

The present invention makes it possible for unskilled to inspect the total surface of a liquid crystal panel accurately in short time. It is defined that a liquid crystal panel can be divided into a single part which is a constituent, isolable, and an inspectable area, and that the single part to be "unit area of image" which is defined as a pattern to be inspected. Before the inspection, a unit area of an image without defect is selected from a liquid crystal panel to be inspected. The upper limit reference pattern and the lower limit reference pattern are generated by giving the maximal brightness in a convolution and adding the predetermined brightness and by giving the minimal brightness in the convolution and subtracting the predetermined brightness, respectively, to each pixel of the convolution. Comparing a brightness of each pixel of the upper limit and the lower limit reference pattern with a brightness of a pixel of a pattern to be inspected corresponding to it, the liquid crystal panel to be inspected is judged to be up to standard when more than a predetermined number of pixels are within the range between the upper limit and the lower limit brightness of the reference pattern.

What is claimed is: 
     
       1. A method for inspecting a liquid crystal panel, said liquid crystal panel being divided into a plurality of single parts which are each constituent, isolable, and inspectable, each of said single parts being a unit area of an image which is a pattern to be inspected to judge whether it is defective by comparing said pattern to be inspected with a reference pattern recorded beforehand, said method comprising the steps of: selecting a unit area of an image without a defect from a liquid crystal panel to be inspected;   generating an upper limit reference pattern from a reference pattern by adding a predetermined upper limit brightness to each pixel of said reference pattern;   setting a brightness of each pixel in said upper limit brightness pattern equal to a maximum pixel brightness in a neighborhood of said pixel to obtain a processed upper limit brightness pattern;   generating a lower limit reference pattern from said reference pattern by subtracting a predetermined lower limit brightness to each pixel of said reference pattern;   setting a brightness of each pixel in said lower limit brightness pattern equal to a minimum pixel brightness in a neighborhood of said pixel to obtain a processed lower limit brightness pattern;   comparing a brightness of each pixel of the processed upper limit reference pattern with a brightness of a corresponding pixel of a pattern to be inspected;   comparing a brightness of each pixel of the processed lower limit reference pattern with a brightness of a corresponding pixel of a pattern to be inspected;   determining that the liquid crystal panel to be inspected is acceptable when more than a predetermined number of pixels have a brightness between brightnesses of corresponding pixels in said processed upper limit reference pattern and said processed lower limit reference pattern and that the liquid crystal panel to be inspected is not acceptable when less than said predetermined number of pixels have a brightness between the brightnesses of said corresponding pixels.   
     
     
       2. A method for inspecting a liquid crystal panel as claimed in claim 1, wherein said unit area of image comprises a predetermined number of cells. 
     
     
       3. A method for inspecting a liquid crystal panel as claimed in claim 1, further comprising a step of: normalizing pixel brightnesses in said panel to be inspected so that a mean pixel brightness is 128.   
     
     
       4. A method for inspecting a liquid crystal panel as claimed in claim 1, said upper limit brightness pattern setting step comprising a step of: swelling brightnesses of pixels in the upper limit reference pattern.   
     
     
       5. A method for inspecting a liquid crystal panel as claimed in claim 1, said lower limit brightness pattern setting step comprising a step of: shrinking brightnesses of pixels in the lower limit reference pattern.   
     
     
       6. A method for inspecting a liquid crystal panel as claimed in claim 1, further comprising a step of: selecting said reference pattern from a plurality of reference patterns, said reference pattern having a maximum number of similar characteristics with said pattern to be displayed.   
     
     
       7. A method for inspecting a liquid crystal panel as claimed in claim 1, said method further comprising the steps of: normalizing pixel brightness in said reference pattern by adding or subtracting a constant value from each pixel in said reference pattern; and   adjusting pixel brightness in said pattern to be inspected by adding or subtracting said constant value from each pixel in said pattern to be inspected.